Replace per-endpoint market name matching with unified contract code
lookup on the legacy Socrata endpoint (6dca-aqww.json). COMEX became
"COMMODITY EXCHANGE INC.", CBOT became "CHICAGO BOARD OF TRADE", and
the disaggregated endpoints stopped receiving Natural Gas / financial
instruments after Feb 2022. Contract codes (067651, 023651, etc.) are
stable across rebranding. Fetch now returns 19/19 markets dated
2026-06-16.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
c9f7757a86